The present invention relates to materials for a luminescence element which can emit light by converting electric energy to light (e.g., an organic electroluminescence (EL) element) and relates to the luminescence element, and in particular, the present invention relates to a luminescence element which can be suitably used in various fields such as display elements, displays, back lights, electrophotography, illumination light sources, recording light sources, reading light sources, indicators, signboards, interior design, etc.
In recent years, various display elements have been researched and developed actively. Above all, organic EL elements can give high luminance at low voltage and have attracted public attention as promising display elements. For example, an EL element in which an organic thin film is formed by vapor deposition of an organic compound is known (Applied Physics Letters, Vol. 51, p. 913 (1987)). As compared with conventionally used single layer type elements, luminous characteristics of the organic EL element described in the above literature have been drastically improved by laminating tris (8-hydroxyquinolinate)aluminum complex (Alq) as an electron-transporting material with a hole-transporting material (an amine compound).
A method of doping a fluorescent dye is known as a means for further improving luminous efficiency of the above laminate type EL element. For example, the luminous efficiency of the organic EL element doped with a coumarin dye as described in Journal of Applied Physics, Vol. 65, p. 3610 (1989) has been widely improved as compared with elements which are not doped. In this case, light having a desired wavelength can be taken out by varying the kind of the fluorescent compound to be used. However, in the case where Alq is used as an electron-transporting material, if driving voltage is increased to obtain high luminance, green emission of Alq comes to be observed in addition to the emission of the doped fluorescent compound, as a result, there arises such a problem as color purity in the case of blue or red emission is reduced. Therefore, the development of host materials which do not generate color purity reduction has been desired.
Although organic EL elements which so far have been developed are certainly improved in light emission intensity and durability by the improvement of the constitution of elements and materials, they do not have sufficient performances yet considering various developments of applications. For example, conventional metal complexes, such as Alq, are chemically labile at electroluminescence, and inferior in adhesion to the cathode, and the problem of deterioration of elements has not yet been solved. Moreover, in the case of Alq, as it is a complex having oxine as a ligand, there is some fear in the safety of the material. Therefore, development of the electron-transporting materials of organic EL elements which are environmentally benign has been required.
On the other hand, it is a laminated element that has realized high luminance emission in an organic EL element byvacuum deposition of organic materials, but the production of elements by a coating system is preferred from the viewpoint of simplification of producing step, processability and realization of large area elements. However, elements which so far have been produced by a coating system are inferior to those produced by a vacuum deposition system in luminance and luminous efficiency, therefore, high luminance and luminescence with high efficiency have been left as problems to be solved.
A first object of the present invention is to provide a material for a luminescence element which shows good luminous characteristics and is excellent in stability by repeating use and a luminescence element.
A second object of the present invention is to provide a luminescence element which is excellent in color purity and a material for the luminescence element which makes it possible.
These objects of the present invention have been achieved the following means.
(1) A material for a luminescence element, which is a compound represented by the following formula (K-Ic), (K-Id) or K-Ie): 
wherein Ra1 represent an aliphatic hydrocarbon group having 6 or less carbon atoms, an arly group, or a heterocyclic group; M represents a metal ion; n represents an integer of from 1 to 4; and Ra1, Ra2, Ra3, Ra4, Ra5 and Ra6 each represents a hydrogen atom or a substituent; 
wherein Ra1 represents an aliphatic hydrocarbon group having from 9 to 30 carbon atoms, an aryl group, or a heterocyclic group; M represents a metal ion; n represents an integer of from 1 to 4; and Ra1, Ra2, Ra3, Ra4, Ra5 and Ra6 each represents a hydrogen atom or a substituent; or 
wherein Ra1 represents an aliphatic hydrocarbon group, an aryl group, or a heterocyclic group, each of which has a halogen atom, an alkoxyl group, an aryloxy group or a heterocyclic oxy group as a substituent; M represents a metal ion; n represents an integer of from 1 to 4; and Ra1, Ra2, Ra3, Ra4, Ra5 and Ra6 each represents a hydrogen atom or a substituent.
(2) The material for a luminescence element as in the above item (1), wherein said compound contains a divalent, trivalent, or tetravalent metal ion.
(3) The material for a luminescence element as in the above item (1), wherein said compound contains a zinc ion.
(4) A material for a luminescence element which is a compound having a partial structure represented by the following formula (I): 
wherein Q1 represents an atomic group necessary to form a 5- or 6-membered nitrogen-containing aromatic heterocyclic ring; Q2 represents an atomic group necessary to form a 5- or 6-membered aromatic ring; X and Y each represents a carbon atom or a nitrogen atom; and Z represents SO1R1, COR2 or POR3(R4), wherein R1, R2, R3 and R4 each represents an aliphatic hydrocarbon group, an aryl group, a heterocyclic group, an amino group, an alkoxyl group, an aryloxy group or a heterocyclic oxy group, wherein said compound is negative in xe2x80x9cReverse-Mutation Assay in Bacteriaxe2x80x9d provided by xe2x80x9cLaw Concerning the Examination and Regulation of Manufacture, etc., of Chemical Substancesxe2x80x9d.
(5) A material for a luminescence element which is a compound having a partial structure represented by the following formula (I): 
wherein Q1 represents an atomic group necessary to form a 5- or 6-membered nitrogen-containing aromatic heterocyclic ring; Q2 represents an atomic group necessary to form a 5- or 6-membered aromatic ring; X and Y each represents a carbon atom or a nitrogen atom; and Z represents SO2R1, COR2 or POR3(R4), wherein R1, R2, R3 and R4 each represents an aliphatic hydrocarbon group, an aryl group, a heterocyclic group, an amino group, an alkoxyl group, an aryloxy group or a heterocyclic oxy group, wherein said compound has a glass transition temperature of 130xc2x0 C. or more.
(6) A luminescence element comprising a pair of electrodes having formed therebetween a luminescence layer or a plurality of organic compound thin film layers comprising a luminescence layer, wherein at least one layer is a layer containing the material for a luminescence element described in the above item (1), (2), (3), (4) or (5).
(7) A luminescence element comprising a pair of electrodes having formed therebetween a luminescence layer or a plurality of organic compound thin film layers comprising a luminescence layer, wherein at least one layer is a layer formed by coating a compound having a partial structure represented by the following formula (I): 
wherein Q1 represents an atomic group necessary to form a 5- or 6-membered nitrogen-containing aromatic heterocyclic ring; Q2 represents an atomic group necessary to form a 5- or 6-membered aromatic ring; X and Y each represents a carbon atom or a nitrogen atom; and Z represents SO2R1, COR2 or POR3(R4), wherein R1, R2, R3 and R4 each represents an aliphatic hydrocarbon group, an aryl group, a heterocyclic group, an amino group, an alkoxyl group, an aryloxy group or a heterocyclic oxy group.
(8) A luminescence element comprising a pair of electrodes having formed therebetween a luminescence layer or a plurality of organic compound thin film layers comprising a luminescence layer, wherein at least one layer is a layer comprising a compound having a partial structure represented by the following formula (I): 
wherein Q1 represents an atomic group necessary to form a 5- or 6-membered nitrogen-containing aromatic heterocyclic ring; Q2 represents an atomic group necessary to form a 5- or 6-membered aromatic ring; X and Y each represents a carbon atom or a nitrogen atom; and Z represents SO2R1, COR2 or POR3(R4), wherein R1, R2, R3 and R4 each represents an aliphatic hydrocarbon group, an aryl group, a heterocyclic group, an amino group, an alkoxyl group, an aryloxy group or a heterocyclic oxy group, having been dispersed in a polymer.
(9) A luminescence element comprising a pair of electrodes having formed therebetween a luminescence layer or a plurality of organic compound thin film layers comprising a luminescence layer, wherein at least one layer contains a compound having a partial structure represented by the following formula (I): 
wherein Q1 represents an atomic group necessary to form a 5- or 6-membered nitrogen-containing aromatic heterocyclic ring; Q2 represents an atomic group necessary to form a 5- or 6-membered aromatic ring; X and Y each represents a carbon atom or a nitrogen atom; and Z represents SO2R1, COR2 or POR3(R4), wherein R1, R2, R3 and R4 each represents an aliphatic hydrocarbon group, an aryl group, a heterocyclic group, an amino group, an alkoxyl group, an aryloxy group or a heterocyclic oxy group, wherein the layer containing said compound further contains at least one kind of other fluorescent compound.
(10) A luminescence element comprising a pair of electrodes having formed therebetween a luminescence layer or a plurality of organic compound thin film layers comprising a luminescence layer, wherein the organic compound thin film layers comprise at least three layers of a hole-transporting layer, a luminescence layer and an electron-transporting layer, said electron-transporting layer comprising at least a compound having a partial structure represented by the following formula (I): 
wherein Q1 represents an atomic group necessary to form a 5- or 6-membered nitrogen-containing aromatic heterocyclic ring; Q2 represents an atomic group necessary to form a 5- or 6-membered aromatic ring; X and Y each represents a carbon atom or a nitrogen atom; and Z represents SO1R1, COR2 or POR3(R4), wherein R1, R2, R3 and R4 each represents an aliphatic hydrocarbon group, an aryl group, a heterocyclic group, an amino group, an alkoxyl group, an aryloxy group or a heterocyclic oxy group.
(11) The luminescence element as in the above item (10), wherein the electron-transporting layer has a film thickness of from 1 to 80 nm.
(12) The luminescence element as in the above item (10), wherein the luminescence layer comprises a single compound.
(13) The luminescence element as in the above item (7), wherein said compound is a metal complex having a compound having a partial structure represented by formula (I) as a ligand.
(14) The luminescence element as in the above item (7), wherein said compound is a metal complex represented by the following formula (K-I): 
wherein Q1 represents an atomic group necessary to form a 5- or 6-membered nitrogen-containing aromatic heterocyclic ring; Q2 represents an atomic group necessary to form a 5- or 6-membered aromatic ring; X and Y each represents a carbon atom or a nitrogen atom; Z represents SO2R1, COR2 or POR3(R4), wherein R1, R2, R3 and R4 each represents an aliphatic hydrocarbon group, an aryl group, a heterocyclic group, an amino group, an alkoxyl group, an aryloxy group or a heterocyclic oxy group; M represents a metal ion; and n represents an integer of from 1 to 4.
(15) The luminescence element as in the above item (7), wherein said compound is a metal complex represented by the following formula (K-Ia): 
wherein Z represents SO2R1, COR2 or POR3(R4), wherein R1, R2, R3 and R4 each represents an aliphatic hydrocarbon group, an aryl group, a heterocyclic group, an amino group, an alkoxyl group, an aryloxy group or a heterocyclic oxy group; M represents a metal ion; n represents an integer of from 1 to 4; and Ra1, Ra2, Ra3, Ra4, Ra5 and Ra6 each represents a hydrogen atom or a substituent.
(16) The luminescence element as in the above item (7), wherein said compound is represented by the following formula 
wherein Rb1 represents an aliphatic hydrocarbon group, an aryl group, or a heterocyclic group; M represents a metal ion; n represents an integer of from 1 to 4; and Ra1, Ra2, Ra3, Ra4, Ra5 and Ra6 each represents a hydrogen atom or a substituent.
The present invention is described in detail below.
In the first place, the compound which has a partial structure represented by formula (I) is described.
Q1 represents an atomic group necessary to form a 5- or 6-membered nitrogen-containing aromatic heterocyclic ring. Examples of 5- or 6-membered nitrogen-containing aromatic heterocyclic ring include pyrrole, imidazole, pyrazole, pyridine, pyrazine, pyrimidine, pyridazine, thiazole, isothiazole, oxazole, isoxazole, selenazole, and triazine, preferably pyridine, pyrazine, pyrimidine, and pyridazine, more preferably pyridine and pyrazine, and particularly preferably pyridine.
The 5- or 6-membered nitrogen-containing aromatic heterocyclic ring represented by Q1 may have a substituent. Examples of substituents include, e.g., an alkyl group (preferably having from 1 to 30, more preferably from 1 to 20, and particularly preferably from 1 to 10, carbon atoms, e.g., methyl, ethyl, isopropyl, tert-butyl, n-octyl, n-decyl, n-hexadecyl, cyclopropyl, cyclopentyl, cyclohexyl), an alkenyl group (preferably having from 2 to 30, more preferably from 2 to 20, and particularly preferably from 2 to 10, carbon atoms, e.g., vinyl, allyl, 2-butenyl, 3-pentenyl), an alkynyl group (preferably having from 2 to 30, more preferably from 2 to 20, and particularly preferably from 2 to 10, carbon atoms, e.g., propargyl, 3-pentynyl), an aryl group (preferably having from 6 to 30, more preferably from 6 to 20, and particularly preferably from 6 to 12, carbon atoms, e.g., phenyl, p-methylphenyl, naphthyl), an amino group (preferably having from 0 to 30, more preferably from 0 to 20, and particularly preferably from 0 to 10, carbon atoms, e.g., amino, methylamino, dimethylamino, diethylamino, dibenzylamino, diphenylamino, ditolylamino), an alkoxyl group (preferably having from 1 to 30, more preferably from 1 to 20, and particularly preferably from 1 to 10, carbon atoms, e.g., methoxy, ethoxy, butoxy, 2-ethylhexyloxy), an aryloxy group (preferably having from 6 to 30, more preferably from 6 to 20, and particularly preferably from 6 to 12, carbon atoms, e.g., phenyloxy, 1-naphthyloxy, 2-naphthyloxy), an acyl group (preferably having from 1 to 30, more preferably from 1 to 20, and particularly preferably from 1 to 12, carbon atoms, e.g., acetyl, benzoyl, formyl, pivaloyl), an alkoxycarbonyl group (preferably having from 2 to 30, more preferably from 2 to 20, and particularly preferably from 2 to 12, carbon atoms, e.g., methoxycarbonyl, ethoxycarbonyl), an aryloxycarbonyl group (preferably having from 7 to 30, more preferably from 7 to 20, and particularly preferably from 7 to 12, carbon atoms, e.g., phenyloxycarbonyl), an acyloxy group (preferably having from 2 to 30, more preferably from 2 to 20, and particularly preferably from 2 to 10, carbon atoms, e.g., acetoxy, benzoyloxy), an acylamino group (preferably having from 2 to 30, more preferably from 2 to 20, and particularly preferably from 2 to 10, carbon atoms, e.g., acetylamino, benzoylamino), an alkoxycarbonylamino group (preferably having from 2 to 30, more preferably from 2 to 20, and particularly preferably from 2 to 12, carbon atoms, e.g., methoxycarbonylamino), an aryloxycarbonylamino group (preferably having from 7 to 30, more preferably from 7 to 20, and particularly preferably from 7 to 12, carbon atoms, e.g., phenyloxycarbonylamino), a sulfonylamino group (preferably having from 1 to 30, more preferably from 1 to 20, and particularly preferably from 1 to 12, carbon atoms, e.g., methanesulfonylamino, benzenesulfonylamino), a sulfamoyl group (preferably having from 0 to 30, more preferably from 0 to 20, and particularly preferably from 0 to 12, carbon atoms, e.g., sulfamoyl, methylsulfamoyl, dimethylsulfamoyl, phenylsulfamoyl), a carbamoyl group (preferably having from 1 to 30, more preferably from 1 to 20, and particularly preferably from 1 to 12, carbon atoms, e.g., carbamoyl, methylcarbamoyl, diethylcarbamoyl, phenylcarbamoyl), an alkylthio group (preferably having from 1 to 30, more preferably from 1 to 20, and particularly preferably from 1 to 12, carbon atoms, e.g., methylthio, ethylthio), an arylthio group (preferably having from 6 to 30, more preferably from 6 to 20, and particularly preferably from 6 to 12, carbon atoms, e.g., phenylthio), a sulfonyl group (preferably having from 1 to 30, more preferably from 1 to 20, and particularly preferably from 1 to 12, carbon atoms, e.g., mesyl, tosyl), a sulfinyl group (preferably having from 1 to 30, more preferably from 1 to 20, and particularly preferably from 1 to 12, carbon atoms, e.g., methanesulfinyl, benzenesulfinyl), a ureido group (preferably having from 1 to 30, more preferably from 1 to 20, and particularly preferably from 1 to 12, carbon atoms, e.g., ureido, methylureido, phenylureido), a phosphoric acid amido group (preferably having from 1 to 30, more preferably from 1 to 20, and particularly preferably from 1 to 12, carbon atoms, e.g., diethylphosphoric acid amido, phenylphosphoric acid amido), a hydroxyl group, a mercapto group, ahalogenatom (e.g., fluorine, chlorine, bromine, iodine), a cyano group, a sulfo group, a carboxyl group, a nitro group, a hydroxamic acid group, a sulfino group, ahydrazino group, an imino group, a heterocyclic group (preferably having from 1 to 30, and more preferably from 1 to 12, carbon atoms, as hetero atoms, e.g., nitrogen, oxygen, sulfur can be exemplified, specifically, imidazolyl, pyridyl, quinolyl, furyl, piperidyl, morpholino, benzoxazolyl, benzimidazolyl, benzothiazolyl can be exemplified) and a silyl group (preferably having from 3 to 40, more preferably from 3 to 30, and particularly preferably from 3 to 24, carbon atoms, e.g., trimethylsilyl, triphenylsilyl). These substituents may further be substituted. When there are two or more substituents, they may be the same or different. Substituents may be linked to each other to form a ring, if possible.
Preferred examples of substituents include an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an amino group, an alkoxyl group, an aryloxy group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyloxy group, an acylamino group, an alkoxycarbonylamino group, an aryloxycarbonylamino group, a sulfonylamino group, a sulfamoyl group, a carbamoyl group, an alkylthio group, an arylthio group, a sulfonyl group, a halogen atom, a cyano group, a carboxyl group, and a heterocyclic group, more preferred substituents include an alkyl group, an alkenyl group, an aryl group, a halogen atom, a cyano group, and a heterocyclic group, still more preferred substituents include an alkyl group, an alkenyl group, an aryl group, and a heterocyclic group, and particularly preferred substituents are an alkyl group, an alkenyl group, an aryl group, and an aromatic heterocyclic group.
Q2 represents an atomic group necessary to form a 5- or 6-membered aromatic ring. The aromatic ring formed by Q2 is an aryl group or an aromatic heterocyclic group, e.g., benzene, pyrrole, imidazole, pyrazole, pyridine, pyrazine, pyrimidine, pyridazine, thiazole, isothiazole, oxazole, isoxazole, selenazole, and triazine, preferably benzene, pyridine, pyrazine, pyrimidine, and pyridazine, more preferably benzene and pyridine, and particularly preferably benzene.
The 5- or 6-membered aromatic ring represented by Q2 may have a substituent. The same groups described as substituents for Q1 can be applied to substituents for Q2 and preferred range is also the same. Substituents may be linked to each other to form a ring, if possible.
X and Y each represents a carbon atom or a nitrogen atom. Preferably, at least either of X or Y represents a carbon atom, more preferably both X and Y represent a carbon atom, or X represents a nitrogen atom and Y represents a carbon atom, and still more preferably both X and Y represent a carbon atom.
Z represents SO2R1, COR2 or POR3(R4) (wherein R1, R2, R3 and R4 each represents an aliphatic hydrocarbon group, an aryl group, a heterocyclic group, an amino group, an alkoxyl group, an aryloxy group or a heterocyclic oxy group).
Examples of the aliphatic hydrocarbon groups represented by R1, R2, R3 and R4 preferably include an alkyl group (preferably having from 1 to 20, more preferably from 1 to 12, and particularly preferably from 1 to 8, carbon atoms, e.g., methyl, ethyl, isopropyl, tert-butyl, n-octyl, n-decyl, n-hexadecyl, cyclopropyl, cyclopentyl, cyclohexyl), an alkenyl group (preferably having from 2 to 20, more preferably from 2 to 12, and particularly preferably from2 to 8, carbon atoms, e.g., vinyl, allyl, 2-butenyl, 3-pentenyl), and an alkynyl group (preferably having from 2 to 20, more preferably from 2 to 12, and particularly preferably from 2 to 8, carbon atoms, e.g., propargyl, 3-pentynyl), and more preferably include an alkyl group and an alkenyl group.
The aryl groups represented by R1, R2, R3 and R4 preferably have from 6 to 30, more preferably from 6 to 20, and particularly preferably from 6 to 12, carbon atoms, e.g., phenyl, 4-methylphenyl, 4-methoxyphenyl, 3-trifluoromethylphenyl, pentafluorophenyl, 1-naphthyl, and 2-naphthyl can be exemplified.
The heterocyclic groups represented by R1, R2, R3 and R4 are monocyclic or condensed heterocyclic groups preferably having from 1 to 20, more preferably from 1 to 12, and still more preferably from 2 to 10, carbon atoms. The heterocyclic groups represented by R1, R2, R3 and R4 are preferably aromatic heterocyclic groups containing at least one nitrogen, oxygen, sulfur, or selenium atom. Specific examples of heterocyclic groups represented by R1, R2, R3 and R4 include, e.g., pyrrolidine, piperidine, pyrrole, furan, thiophene, imidazoline, imidazole, benzimidazole, naphthimidazole, thiazolidine, thiazole, benzothiazole, naphthothiazole, isothiazole, oxazoline, oxazole, benzoxazole, naphthoxazole, isoxazole, selenazole, benzoselenazole, naphthoselenazole, pyridine, quinoline, isoquinoline, indole, indolenine, pyrazole, pyrazine, pyrimidine, pyridazine, triazine, indazole, purine, phthalazine, naphthyridine, quinoxaline, quinazoline, cinnoline, pteridine, phenanthridine, pteridine, phenanthroline, and tetraazaindene, preferably furan, thiophene, pyridine, quinoline, pyrazine, pyrimidine, pyridazine, triazine, phthalazine, naphthyridine, quinoxaline, and quinazoline, and more preferably furan, thiophene, pyridine, and quinoline.
The amino groups represented by R1, R2, R3 and R4 preferably have from 0 to 20, more preferably from 1 to 16, and particularly preferably from 1 to 12, carbon atoms, e.g., amino, methylamino, dimethylamino, diethylamino, dibenzylamino, phenylamino and diphenylamino can be exemplified.
The alkoxyl groups represented by R1, R2, R3 and R4 preferably have from 1 to 20, more preferably from 1 to 16, and particularly preferably from 1 to 12, carbon atoms, e.g., methoxy, ethoxy, butoxy, and 2-ethylhexyloxy can be exemplified.
The aryloxy groups represented by R1, R2, R3 and R4 preferably have from 6 to 20, more preferably from 6 to 16, and particularly preferably from 6 to 12, carbon atoms, e.g., phenyloxy, 4-methoxyphenyloxy, 1-naphthyloxy and 2-naphthyloxy can be exemplified.
The heterocyclic oxy groups represented by R1, R2, R3 and R4 preferably have from 1 to 20, more preferably from 2 to 16, and particularly preferably from 2 to 12, carbon atoms, e.g., pyridyloxy and quinolyloxy can be exemplified.
R1, R2, R3 and R4 each may have a substituent. The same groups described as substituents for Q1 can be applied to the substituents for R1, R2, R3 and R4.
R1 and R2 each preferably represents an aliphatic hydrocarbon group, an aryl group, or a heterocyclic group, and more preferably represents an alkyl group, an aryl group, or an aromatic heterocyclic group.
R3 and R4 each preferably represents an aliphatic hydrocarbon group, an aryl group, a heterocyclic group, an alkoxyl group, an aryloxy group, or a heterocyclic oxy group, more preferably represents an alkoxyl group or an aryloxy group, and still more preferably represents an aryloxy group.
Z preferably represents SO2R1, more preferably represents SO2R5 (wherein R5 represents an aliphatic hydrocarbon group, an aryl group, or a heterocyclic group), and still more preferably represents SO2R6 (wherein R6 represents an aliphatic hydrocarbon group, an aryl group, or an aromatic heterocyclic group).
The compound having a partial structure represented by formula (I) is preferably a metal complex having a compound having a partial structure represented by formula (I) as a ligand, and more preferably a metal complex represented by the following formula (K-I). 
wherein Q1, Q2, X, Y and Z have the same meaning as Q1, Q2, X, Y and Z in formula (I) and preferred ranges of them are also the same.
M represents a metal ion, preferably represents a divalent to tetravalent metal ion, and more preferably a divalent or trivalent metal ion. Specific examples of metal ions represented by M include a beryllium ion, a magnesium ion, a calcium ion, an aluminum ion, a gallium ion, an indium ion, a zirconium ion, a zinc ion, an iron ion, a cobalt ion, a nickel ion, a copper ion, a platinum ion, a palladium ion, a tin ion, a strontium ion, a scandium ion, a silicon ion, a germanium ion, an europium ion, and a terbium ion, preferred examples are a beryllium ion, a magnesium ion, an aluminum ion, a gallium ion, and a zinc ion, more preferred are a beryllium ion, an aluminum ion, and a zinc ion, and still more preferred is a zinc ion. n represents an integer of from 1 to 4 and it varies by the valence of the metal ion. n preferably represents from 2 to 4, and more preferably 2 or 3. When n is from 2 to 4, a plurality of ligands of the metal complex may be the same or different from each other.
The compound represented by formula (K-I) is more preferably represented by formula (K-Ia): 
wherein Z has the same meaning as Z in formula (I), and preferred range is also the same. M and n have the same meaning as M and n in formula (K-I) and preferred ranges of them are also the same.
Ra1, Ra2, Ra3, Ra4, Ra5 and Ra6 each represents a hydrogen atom or a substituent. As the examples of the substituents, those described as the substituents for the ring formed by Q1 in formula (I) can be applied, and preferred ranges of them are also the same.
The compound represented by formula (K-I) is more preferably represented by formula (K-Ib): 
wherein M, n, Ra1, Ra2, Ra3, Ra4, Ra5 and Ra6 have the same meaning respectively as those in formula (K-Ia) and respective preferred ranges are also the same; Rb1 represents an aliphatic hydrocarbon group, an aryl group, or a heterocyclic group, and these aliphatic hydrocarbon group, aryl group, and heterocyclic group have the same meaning as the aliphatic hydrocarbon group, the aryl group, and the heterocyclic group represented by R1, R2, R3 and R4 in formula (I), and respective preferred ranges are also the same; and Rb1 and Ra6 may be linked to form a ring.
Of the compounds represented by formula (K-I), when an organic layer is formed by vapor deposition, the compound represented by formula (K-Ic) is preferably used, and when an organic layer is formed by coating, the compound represented by formula (K-Id) is preferably used: 
wherein M, n, Ra1, Ra2, Ra3, Ra4, Ra5 and Ra6 have the same meaning respectively as those in formula (K-Ia) and respective preferred ranges are also the same; Rc1 represents an aliphatic hydrocarbon group having 6 or less carbon atoms, an aryl group, or a heterocyclic group, wherein the aryl group and the heterocyclic group have the same meaning respectively as those represented by R1 to R4 in formula (I).
Specific examples of Rc1 include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, butenyl, phenyl, furyl, thienyl, pyridyl, pyradinyl, pyrimidyl, imidazolyl, thiazolyl, and oxazolyl, preferably methyl, ethyl, phenyl, and thienyl, more preferably methyl, phenyl, and thienyl, and still more preferably phenyl. Rc1 may have a substituent, and those exemplified as the substituents for Q1 can be applied as the substituent for Rc1. Rc1 and Ra6 may be linked to form a ring; 
wherein M, n, Ra1, Ra2, Ra3, Ra4, Ra5 and Ra6 have the same meaning respectively as those in formula (K-Ia) and respective preferred ranges are also the same; Rd1 represents an aliphatic hydrocarbon group having from 9 to 30 carbon atoms (e.g., n-nonyl, n-decyl, n-dodecyl, n-hexadecyl, n-octadecyl, 3-[2,5-bis(1,1-dimethylpropyl)phenoxy]propyl, 4-[2,5-bis(1,1,3,3-tetramethylbutyl)phenoxy]butyl), an aryl group, or a heterocyclic group. The aryl group and the heterocyclic group have the same meaning respectively as those represented by R1 to R4 in formula (I).
The aliphatic hydrocarbon group, the aryl group, or the heterocyclic group represented by Rd1 may each have a substituent, e.g., those exemplified as the substituents for Q1 can be applied as the substituent for Ra1. Rd1 preferably represents an aliphatic hydrocarbon group having from 9 to 30 carbon atoms including a substituent or an aryl group, more preferably an aliphatic hydrocarbon group having from 9 to 20 carbon atoms or an aryl group, and still more preferably an alkyl group having from 9 to 20 carbon atoms or phenyl group.
The compound represented by formula (K-I) is particularly preferably represented by formula (K-Ie): 
wherein M, n, Ra1, Ra2, Ra3, Ra4, Ra5 and Ra6 have the same meaning respectively as those in formula (K-Ia) and respective preferred ranges are also the same; Re1 represents an aliphatic hydrocarbon group, an aryl group, or a heterocyclic group each of which has a halogen atom, an alkoxyl group, an aryloxy group or a heterocyclic oxy group as a substituent. The aliphatic hydrocarbon group, the aryl group and the heterocyclic group have the same meaning respectively as those represented by R1 to R4 in formula (I).
The halogen atom is preferably a fluorine atom or a chlorine atom, and more preferably a fluorine atom. The alkoxyl group is preferably an alkoxyl group having 1 to 30, more preferably from 1 to 20, and particularly preferably from 1 to 10, carbon atoms, e.g., methoxy, ethoxy, butoxy, 2-ethylhexyloxy. The aryloxy group is preferably an aryloxy group having from 6 to 30, more preferably from 6 to 20, and particularly preferably from 6 to 12, carbon atoms, e.g., phenyloxy, 1-naphthyloxy, 2-naphthyloxy. The heterocyclic oxy group is preferably a heterocyclic oxy group having from 1 to 30, more preferably from 1 to 12, and particularly preferably from 1 to 10, carbon atoms, and a nitrogen atom, an oxygen atom, a sulfur atom are contained as a hetero atom, e.g., pyridyloxy, quinolyloxy can be exemplified.
The aliphatic hydrocarbon group, the aryl group, or the heterocyclic group represented by Re1 may each have a substituent other than a halogen atom, an alkoxyl group, an aryloxy group or a heterocyclic oxy group, and those exemplified as the substituents for Q1 can be applied as the substituent in such a case.
Re1 preferably represents an aliphatic hydrocarbon group or an aryl group substituted with an alkoxyl group or an aryloxy group, more preferably an aryl group substituted with an alkoxyl group, and still more preferably a phenyl group substituted with an alkoxyl group.
A more preferred compound according to the present invention is a compound which is negative in xe2x80x9cReverse-Mutation Assay in Bacteriaxe2x80x9d provided by xe2x80x9cLaw Concerning the Examination and Regulation of Manufacture, etc., of Chemical Substancesxe2x80x9d, and a compound having a glass transition temperature of not lower than 130xc2x0 C. is preferred in view of the durability of a luminescence element.
The compound represented by formula (I), (K-I), (K-Ia), (K-Ib), (K-Ic), (K-Id) or (K-Ie) may be a low molecular weight compound, may be a high molecular weight compound in which the residue represented by formula (I), (K-I), (K-Ia), (K-Ib), (K-Ic), (K-Id) or (K-Ie) is connected to the polymer main chain, or may be a high molecular weight compound whose main chain has the skeleton of formula (I), (K-I), (K-Ia), (K-Ib), (K-Ic), (K-Id) or (K-Ie). The high molecular weight compound may be a homopolymer or a copolymer with other monomers.
Further, formula (I), (K-I), (K-Ia), (K-Ib), (K-Ic), (K-Id) or (K-Ie) is conveniently represented as an extreme structural formula but the compound may be a tautomer.
Specific examples of the compounds having a partial structure represented by formula (I) according to the present invention are shown below, but the present invention is not limited thereto. 
Further, the above exemplified compounds may have other ligands.
Metal salts for use as a starting material in the synthesis of the metal complex according to the present invention are not particularly restricted, for example, halide (fluoride, chloride, bromide, iodide, etc.), sulfate, carboxylate (acetate, etc.), phosphonate, sulfonate, hydroxide, etc., are suitably used, and nitrate, hydrochloride, sulfate, acetate are preferably used.
The molar ratio of a ligand to a metal salt for use in the synthesis of a metal complex is arbitrarily selected according to the complex to be synthesized. In general, a ligand is used from 0.1 to 10 time mol, preferably from 0.5 to 8 time mol, and still more preferably from 0.5 to 6 time mol, of a metal ion.
Further, a base can be used in the synthesis of a metal complex, e.g., various kinds of inorganic or organic bases. For example, a metal hydroxide (e.g., sodium hydroxide, potassium hydroxide), a metal carbonate (e.g., sodium carbonate, potassium carbonate), a metal hydrogencarbonate (e.g., sodium hydrogencarbonate, potassium hydrogencarbonate), and an organic base (e.g., triethylamine, sodium alkoxide) are preferably used.
The amount of a base is not particularly restricted but is preferably from 0.01 to 30 equivalent, more preferably from 1 to 10 equivalent, based on the ligand.
Solvents may be used in the synthesis of a metal complex. Solvents are not particularly limited, for example, water, alcohols (e.g., methanol, ethanol, 2-propanol), esters (e.g., ethyl acetate), ethers (e.g., diethyl ether, tetrahydrofuran, 1,4-dioxane), amides (e.g., dimethylformamide, dimethylacetamide), nitriles (e.g., acetonitrile), ketones (e.g., acetone, cyclohexanone), hydrocarbons (e.g., hexane, benzene, toluene), halogenated hydrocarbons (e.g., dichloromethane, chloroform, 1,2-dichloroethane), carboxylic acids (e.g., acetic acid) can be used. These solvents may be used as mixtures. Preferred solvents are alcohols, ethers and ketones, more preferred are alcohols, and particularly preferred are methanol, ethanol and 2-propanol.
The reaction temperature in synthesis of a metal complex is not particularly restricted but is preferably from 10 to 150xc2x0 C., more preferably from 10 to 100xc2x0 C., and most preferably from 10 to 80xc2x0 C.